Solid State Relay Power Harvesting With Capacitor Threshold Control
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Solution Overview
Problem
Existing relay circuits that derive power from a load face challenges in determining the optimal time to recharge a supply capacitor, as this time depends on various factors like load inductance, capacitor size, current, and resistance, leading to incomplete charging or unnecessary disconnection.
Innovation Solution
A solid state relay circuit that includes a control circuit to automatically turn the relay on and off based on capacitor voltage thresholds, ensuring sufficient charge is maintained by toggling the relay between ON and OFF states when the voltage falls below a low threshold and rises above a high threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the relay is turned off for a fixed time to recharge the capacitor, then the capacitor can be recharged, but the load may be disconnected for too much time or the capacitor may not charge completely
Solution Approach 1:
The patent implements feedback control by monitoring the capacitor voltage and using it to control the relay switching. The control circuit continuously detects the capacitor voltage level and adjusts the relay state accordingly - turning the relay off when voltage drops below a first threshold to allow recharging, and turning it on when voltage rises above a second threshold to restore load connection. This closed-loop feedback mechanism eliminates the need for fixed timing, ensuring the relay remains off only long enough to adequately recharge the capacitor without unnecessarily disconnecting the load.
Solution Approach 2:
The patent transitions from a static fixed-time switching approach to a dynamic voltage-threshold-based switching approach. The relay switching duration is no longer predetermined but dynamically adjusted based on the actual capacitor voltage level. This dynamic control adapts to varying operating conditions such as different load inductances, capacitor sizes, and current levels, optimizing both charging completeness and load connection time for each specific scenario.
2Reliability
If the relay switching time is extended to ensure complete capacitor charging, then the capacitor charges fully, but the load remains disconnected longer than necessary
Solution Approach 1:
The feedback mechanism monitors capacitor voltage in real-time and dynamically determines the optimal switching moment. When the capacitor voltage reaches the second threshold (indicating sufficient charge), the control circuit immediately triggers the relay to close, restoring load connection. This feedback-driven approach ensures power supply stability by guaranteeing adequate charging while maximizing load operation continuity by minimizing unnecessary disconnection time.
Solution Approach 2:
The patent changes the control parameter from fixed time duration to voltage threshold levels. By setting appropriate voltage thresholds (first threshold for turning off, second threshold for turning on), the system adapts to different operating conditions including variations in load inductance, capacitor capacity, and current levels. This parameter-based control optimizes the balance between ensuring sufficient charge accumulation and minimizing load disconnection duration.
3Device complexity
If the relay switching is based on fixed timing, then the control is simple, but the charging time may not be sufficient or excessive
Solution Approach 1:
The control circuit incorporates voltage detection and comparison functionality that, while adding some complexity, provides robust and adaptive control. The feedback mechanism compares the actual capacitor voltage against predetermined thresholds and automatically adjusts switching behavior accordingly. This ensures reliable and adequate charging under varying conditions (different load inductances, capacitor sizes, current levels) while maintaining relatively simple control logic based on voltage threshold comparisons.
Solution Approach 2:
The control circuit performs self-adjustment based on capacitor voltage feedback without requiring external timing inputs or complex control algorithms. The system uses the capacitor's own voltage state to determine switching actions - when voltage drops below the first threshold, the relay turns off to allow recharging; when voltage rises above the second threshold, the relay turns on to restore load connection. This self-service approach enhances charging reliability while keeping the control mechanism relatively simple.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach optimizes the charging process by maintaining the relay in the ON state for the necessary time, ensuring the capacitor is fully charged while minimizing unnecessary disconnection of the load, thus providing reliable power to the circuit.
Implementation Method 1
charge a supply capacitor in the power control circuit to a DC voltage using the load voltage when the relay is off
Implementation Method 2
The solid state relay control circuit may be arranged to turn the solid state relay switch to an OFF state when a capacitor voltage of the charging capacitor falls below a low threshold value
Data Source
AI summary
A relay circuit may include a solid state relay switch, coupled to an external voltage line and to an charging capacitor; and a solid state relay control circuit, coupled between the charging capacitor and the solid state relay switch. The solid state relay control circuit may be arranged to: turn the solid state relay switch to an OFF state when a capacitor voltage of the charging capacitor falls below a low threshold value; and change the solid state relay switch from the OFF state to an ON state when the capacitor voltage increases above a high threshold value.